In the last two decades, digital mobile communication technologies have almost fully replaced analog mobile communication systems, commonly referred to as first generation systems. With the early digital communication systems (or second generation systems) such as the Global System for Mobile communication (GSM), a wide-spread acceptance and use of mobile telephony services has begun. Today, third generation systems such as the Universal Mobile Telecommunication System (UMTS) as standardized by the 3rd Generation Partnership Project (3GPP) offer a plethora of sophisticated multimedia features and novel mobile applications including, for example, personal navigation via the Global Positioning System (GPS). Fourth generation technologies are already about to enter the standardization phase.
Since the earliest Release 99 of the 3GPP specifications, UMTS uses W-CDMA (Wideband Code Division Multiple Access) as high speed transmission protocol on the air interface. The performance of the W-CDMA-based UMTS standard is extended and improved by a collection of technologies known as High Speed Packet Access (HSPA) protocols. Two different protocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), have been standardized by 3GPP. HSPDA is part of the UMTS specifications since Release 5, while the specifications for HSUPA are included in Release 6.
A further enhancement of the UMTS standard, Evolved HSPA (eHSPA) or HSPA+, will be introduced with Release 7. Evolved HSPA provides even higher data rates on both the uplink and the downlink using sophisticated technologies such as antenna diversity (Multiple Input Multiple Output, or MIMO) and higher order modulation. While eHSPA still relies on W-CDMA, the Long Term Evolution (LTE) project of 3GPP is defining a new air interface that will be implemented with Release 8 of the 3GPP specifications.
The various “Releases” of the 3GPP specifications exist in parallel to provide developers with a stable platform for implementation while at the same time allowing the addition of new technical features. Each Release can be considered as a separate Radio Access Technology (RAT), although it will incorporate certain features of the previous Releases.
The parallel existence of various Releases makes it desirable for a single item of hardware (such as a mobile telephone) to provide support for RATs defined in different Releases. Such multi-Release support increases the overall connectivity. As one example, a multi-Release mobile telephone may automatically perform radio access via an “older” Release RAT if the locally available radio network infrastructure is not compatible with a newer Release RAT also supported by the mobile telephone. Then, an automatic hand-over from the older Release RAT to the newer Release RAT is performed as soon as the mobile telephone enters the coverage area of radio network infrastructure supporting the newer Release RAT.
In mobile telephones, support for a new Release (either singly or in combination with support for one or more previous Releases) also requires a new hardware design. The hardware that needs to be re-designed typically includes Application Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and Digital Signal Processors (DSPs). If, for example, a new Release specifies a more sophisticated modulation scheme, the design of the existing baseband ASIC which only supports the modulation scheme of the previous Release has to be changed. Such a design change involves new Non-Recurring Engineering (NRE) cost. Additionally, the ASIC re-design introduces new technology risks, including ASIC lead time and re-spin efforts resulting from design bugs that are only detected at a late stage of the ASIC development process.
In cases in which the ASIC is re-designed to support the new Release in addition to one or more previous Releases (i.e., to support two or more RATs), additional support for the novel features of the new Release will lead to a larger ASIC die size, which is undesirable for various reasons. Moreover, there is also the risk that the new Release will not be accepted on the market. In such a case, the re-designed ASIC—although also supporting the widely accepted previous Release—can not be cost-efficiently incorporated into end-consumer devices. An ASIC supporting multiple Releases thus generally decreases the technological flexibility of device manufacturers.